4 research outputs found
Experimental investigation on the high-order modes in supercontinuum generation from step-index As-S fibers
Two kinds of step-index As–S fibers have been fabricated by an isolated extrusion method with a numerical aperture (NA) of 0.52, but with different core size of 10 or 50 µm. With a femtosecond laser pumping, their supercontinnum (SC) generation spectra were recorded in order to testify the effect of high-order modes on SC generation. The spectra spanning from 1.0 to 6.7 µm and from 1.5 to 8.6 µm can be obtained in a 16-cm-long fiber with 10 µm-core diameter pumping by central wavelength of 2.9 and 4.0 µm, respectively. The results show that high-order modes would deplete the spectra spanning in red-shifting part. The SC generation in small-core fiber is much more efficient than that in large-core fiber. This is the first comparative investigation on the SC generation from the quasi single- and multi-mode ChG fibers under the same conditions.This work has been supported by the Natural Science Foundation of China (Grant Nos. 61705091, 61775109, 61627815
and 61377099); Zhejiang Provincial Natural Science Foundation of
China (Grant No. LR18F050002); the Opening Project of Key Laboratory of Optoelectronic Detection Materials and Devices of Zhejiang
Province, China (Grant No. 2017004); Program for Science and Technology of Jiaxing, China (Grant No. 2017AY13010); and the K. C.
Wong Magna Fund in Ningbo University, China
The effects of diffusional couplings on compositional trajectories and interfacial free energies during phase separation in a quaternary Ni-Al-Cr-Re model superalloy
The temporal evolution of ordered gamma-prime(L12)-precipitates and the
compositional trajectories during phase-separation of the
gamma(face-centered-cubic(f.c.c.)) and gamma-prime(L12)-phases are studied in a
Ni-0.10Al-0.085Cr-0.02Re(mole-fraction) superalloy, utilizing atom-probe
tomography, transmission electron microscopy, and the Philippe-Voorhees (PV)
coarsening model. As the gamma-prime(L12)-precipitates grow, the excesses of
Ni, Cr and Re, and depletion of Al in the gamma(f.c.c.)-matrix develop as a
result of diffusional fluxes crossing gamma(f.c.c.)/gamma-prime(L12)
heterophase interfaces. The coupling effects on diffusional fluxes was
introduced (PV coarsening model) in terms of the diffusion tensor, D, and the
second-derivative tensor of the molar Gibbs free energies, G", obtained
employing Thermo-Calc and DICTRA calculations. The Gibbs interfacial free
energies are (6.9 +- 1.4) mJ/m2 with all terms in D and G", which changes to
(18.9 +- 2.1) mJ/m2, (37.7 +- 3.3) mJ/m2, and (-7.5 +- 1.2) mJ/m2 without
including the off-diagonal terms in D, G", and both D and G", respectively. The
experimental APT compositional trajectories are displayed and compared with the
PV model in a partial quaternary phase-diagram, employing a tetrahedron. The
compositional trajectories measured by APT exhibit curvilinear behavior in the
nucleation and growth regimes, which become vectors, moving simultaneously
toward the gamma(f.c.c.) and gamma-prime(L12) conjugate solvus-surfaces, for
the quasi-stationary coarsening regime. The compositional trajectories are
compared to the PV model with and without the off-diagonal terms in D and G".
The directions including the off-diagonal terms in D and G" tensors are
consistent with the APT experimental data.Comment: 63 pages, 18 figures, 3table